The aim of this thesis was to develop and evaluate albumin-based conjugates for their use in radiotherapy and antibody-recruiting therapy which may then be combined to enhance therapeutic efficacy of each monotherapy. The approach taken in order to achieve high tumour uptake of the conjugates and minimize doses to healthy tissues involved the intratumoural administration of therapeutic compounds; a technique which has gained popularity in recent years for the treatment of solid tumours. Despite the promise this method of administration holds, it is often limited by the fast clearance of injected compounds from the tumour. Using albumin-based conjugates allows for the exploitation of the enhanced permeation and retention (EPR) effect which aids in the retention of the compound at the site of interest for longer periods of time, thus allowing the opportunity for enhanced therapeutic efficacy.
Bovine serum albumin conjugated with DOTA chelators was first synthesized and found to possess 3.9 ± 0.4 chelates per BSA molecule. Radiolabelling of the compound with lutetium- 177 produced the desired product in radiochemical yields of 74 ±2 % with a radiochemical purity >99%. The stability of the compound was evaluated by monitoring the radiochemical purity over 7 days which was found to be >95% pure over the entirety of the testing period, indicating a stable product. The intratumoural administration of [177Lu]Lu-DOTA-BSA in a triple negative breast cancer (TNBC) tumour model revealed significant tumour retention of 52 ± 12 %ID/g and 35 ± 6 %ID/g at 24 h and 72 h post-injection, respectively, while autoradiography displayed a heterogenous dispersion of the compound throughout the tumour. A multidosing therapy study in which animals received two doses of either 4.44, 5.92, or 7.40 MBq of [177Lu]Lu-DOTA-BSA showed promise, with a strong trend observed between the administration of higher doses and a prolonged lifespan. Histological analysis of tumours excised 7 days post-treatment revealed signs
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of necrosis and apoptosis in tumours treated with 7.40 MBq [177Lu]Lu-DOTA-BSA. These preliminary results prove to be a promising approach for use in combination therapy and may be further optimized to enhance its efficacy as a monotherapy.
Next, the in vivo evaluation of DNP-BSA was carried out to assess using an intratumourally administered, albumin-based platform for antibody-recruiting in a triple negative breast cancer model. A preliminary antibody-recruiting study administering 35 nmol DNP-BSA three times per week unfortunately did not induce slowed tumour growth nor did it have an impact on lifespan. Treated mice were also unable to tolerate repeated doses of the antigen which indicated too high of a concentration and/or dosing frequency was used. A tolerability study was then carried out in order to determine a treatment schedule which did not lead to adverse effects. Mice treated once per week with low (9 nmol) to moderate (17 nmol) doses of DNP-BSA did not display toxic effects but unfortunately did not exhibit a therapeutic effect nor any indication that an adaptive immune response was achieved. These results suggest that further optimization is required prior to use in combination therapy and moderate doses (17 nmol) DNP should be used to investigate a treatment schedule which is able to induce antibody recruitment. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27221 |
| Date | January 2021 |
| Creators | Mercanti, Natalie |
| Contributors | Valliant, John, Sadeghi, Saman, Rullo, Anthony, Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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